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Date: Mon, 17 May 2010 16:17:15 +0200
From: Michael Holzheu <holzheu@...ux.vnet.ibm.com>
To: "Luck, Tony" <tony.luck@...el.com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
"benh@...nel.crashing.org" <benh@...nel.crashing.org>,
"schwidefsky@...ibm.com" <martin.schwidefsky@...ibm.com>,
"heiko.carstens@...ibm.com" <heiko.carstens@...ibm.com>,
"jlan@....com" <jlan@....com>,
"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>
Subject: RE: [PATCH] Use microsecond granularity for taskstats accounting
Hello Tony,
On Fri, 2010-05-14 at 14:28 -0700, Luck, Tony wrote:
> You delete the only users of cputime_to_msecs() ... should
> you also delete the definition from asm-generic/cputime.h?
> Same for the msecs_to_cputime() that had no users.
>
> Is it worth adding the usecs_to_cputime() functions/macros.
> Symmetry is nice (and matches what used to be there, but
> unused code isn't very worthwhile.
Fine, I removed the msecs functions, but I have the feeling that we
should keep the usecs_to_cputime().
Another thing: The power PC implementation of cputime_to_usecs() could
probably be done better. With my patch it still uses only millisecond
granularity. To fix this we probably would have to add a new variable
"__cputime_usec_factor". Not sure, if we should do that.
Here the updated patch:
From: Michael Holzheu <holzheu@...ux.vnet.ibm.com>
The taskstats interface uses microsecond granularity for the user and
system time values. The conversion from cputime to the taskstats values
uses the cputime_to_msecs primitive which effectively limits the
granularity to milliseconds. Add the cputime_to_usecs primitive for
architectures that have better, more precise CPU time values. Remove
cputime_to_msecs primitive because there is no more user left.
Signed-off-by: Michael Holzheu <holzheu@...ux.vnet.ibm.com>
---
arch/ia64/include/asm/cputime.h | 6 +++---
arch/powerpc/include/asm/cputime.h | 12 ++++++------
arch/s390/include/asm/cputime.h | 10 +++++-----
include/asm-generic/cputime.h | 6 +++---
kernel/tsacct.c | 10 ++++------
5 files changed, 21 insertions(+), 23 deletions(-)
--- a/arch/ia64/include/asm/cputime.h
+++ b/arch/ia64/include/asm/cputime.h
@@ -56,10 +56,10 @@ typedef u64 cputime64_t;
#define jiffies64_to_cputime64(__jif) ((__jif) * (NSEC_PER_SEC / HZ))
/*
- * Convert cputime <-> milliseconds
+ * Convert cputime <-> microseconds
*/
-#define cputime_to_msecs(__ct) ((__ct) / NSEC_PER_MSEC)
-#define msecs_to_cputime(__msecs) ((__msecs) * NSEC_PER_MSEC)
+#define cputime_to_usecs(__ct) ((__ct) / NSEC_PER_USEC)
+#define usecs_to_cputime(__usecs) ((__usecs) * NSEC_PER_USEC)
/*
* Convert cputime <-> seconds
--- a/arch/powerpc/include/asm/cputime.h
+++ b/arch/powerpc/include/asm/cputime.h
@@ -124,23 +124,23 @@ static inline u64 cputime64_to_jiffies64
}
/*
- * Convert cputime <-> milliseconds
+ * Convert cputime <-> microseconds
*/
extern u64 __cputime_msec_factor;
-static inline unsigned long cputime_to_msecs(const cputime_t ct)
+static inline unsigned long cputime_to_usecs(const cputime_t ct)
{
- return mulhdu(ct, __cputime_msec_factor);
+ return mulhdu(ct, __cputime_msec_factor) * USEC_PER_MSEC;
}
-static inline cputime_t msecs_to_cputime(const unsigned long ms)
+static inline cputime_t usecs_to_cputime(const unsigned long us)
{
cputime_t ct;
unsigned long sec;
/* have to be a little careful about overflow */
- ct = ms % 1000;
- sec = ms / 1000;
+ ct = us % 1000000;
+ sec = us / 1000000;
if (ct) {
ct *= tb_ticks_per_sec;
do_div(ct, 1000);
--- a/arch/s390/include/asm/cputime.h
+++ b/arch/s390/include/asm/cputime.h
@@ -73,18 +73,18 @@ cputime64_to_jiffies64(cputime64_t cputi
}
/*
- * Convert cputime to milliseconds and back.
+ * Convert cputime to microseconds and back.
*/
static inline unsigned int
-cputime_to_msecs(const cputime_t cputime)
+cputime_to_usecs(const cputime_t cputime)
{
- return cputime_div(cputime, 4096000);
+ return cputime_div(cputime, 4096);
}
static inline cputime_t
-msecs_to_cputime(const unsigned int m)
+usecs_to_cputime(const unsigned int m)
{
- return (cputime_t) m * 4096000;
+ return (cputime_t) m * 4096;
}
/*
--- a/include/asm-generic/cputime.h
+++ b/include/asm-generic/cputime.h
@@ -33,10 +33,10 @@ typedef u64 cputime64_t;
/*
- * Convert cputime to milliseconds and back.
+ * Convert cputime to microseconds and back.
*/
-#define cputime_to_msecs(__ct) jiffies_to_msecs(__ct)
-#define msecs_to_cputime(__msecs) msecs_to_jiffies(__msecs)
+#define cputime_to_usecs(__ct) jiffies_to_usecs(__ct);
+#define usecs_to_cputime(__msecs) usecs_to_jiffies(__msecs);
/*
* Convert cputime to seconds and back.
--- a/kernel/tsacct.c
+++ b/kernel/tsacct.c
@@ -63,12 +63,10 @@ void bacct_add_tsk(struct taskstats *sta
stats->ac_ppid = pid_alive(tsk) ?
rcu_dereference(tsk->real_parent)->tgid : 0;
rcu_read_unlock();
- stats->ac_utime = cputime_to_msecs(tsk->utime) * USEC_PER_MSEC;
- stats->ac_stime = cputime_to_msecs(tsk->stime) * USEC_PER_MSEC;
- stats->ac_utimescaled =
- cputime_to_msecs(tsk->utimescaled) * USEC_PER_MSEC;
- stats->ac_stimescaled =
- cputime_to_msecs(tsk->stimescaled) * USEC_PER_MSEC;
+ stats->ac_utime = cputime_to_usecs(tsk->utime);
+ stats->ac_stime = cputime_to_usecs(tsk->stime);
+ stats->ac_utimescaled = cputime_to_usecs(tsk->utimescaled);
+ stats->ac_stimescaled = cputime_to_usecs(tsk->stimescaled);
stats->ac_minflt = tsk->min_flt;
stats->ac_majflt = tsk->maj_flt;
--
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